1. The Field of the Invention
The present invention relates to a method of thermosiphoning supercritical CO2 in a geothermal energy production system.
2. Background of the Invention
Geothermal energy systems are designed to extract heat from an underground hot rock reservoir. To create a geothermal energy system, a fluid is pumped down into a rock formation through an injection well. This pumping will cause the rock formation to fracture and seal, forming a reservoir. After the reservoir is created, the same fluid or a different working fluid is then pumped into the reservoir and flows across the fractured surfaces of the hot rock reservoir where it is heated by the natural geothermal temperatures within the reservoir. This geothermal heat is transferred to the surface by flowing the working fluid upward through one or more production wells. At the surface, the heated working fluid is used to generate electrical power and then is pumped back into the reservoir via the injection well. This flow is typically carried out in a pressurized, closed-loop circulating operation and requires the use of pumps.
In the industry today, geothermal energy systems mostly use water as the working fluid. However, supercritical carbon dioxide, halogenated hydrocarbon refrigerants, ammonia, mixtures of ammonia and water, or low molecular weight hydrocarbons such as propanes, butanes, and hexanes, and mixtures of these have been theorized to work in geothermal systems as well.
Using supercritical CO2 within a geothermal energy system can be advantageous because supercritical CO2 is generally inert, nonhazardous, provides lower mineral solubility, reduces corrosion, and has faster diffusion rates as compared to water.
The present invention relates to methods for using supercritical CO2 within a geothermal energy system without the use of pumps. The present invention relates to a fluid drive for thermal siphoning supercritical CO2 within the geothermal system and reduces required pumping power.